This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

-- Scan line number of start of swept portion (before is fixed portion)

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

Satellite Altitude in km

Virtual variable.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 1 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1998

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This data set, provided by the Communications Research Centre (CRC) in Ottawa,
Canada, consists of electron density profiles for the ionosphere above the F2
maximum (topside ionosphere). The data were computed from the orginal ionograms
using Jackson's method (Jackson, Proceedings of the IEEE., p. 960, June 1969).
ISIS-1 was launched on 1969-01-30 into an elliptical orbit (500-3500km) with an
inclination of 88.4 degrees and ISIS-2 was launched on 1971-04-01 into an
circular orbit at 1400 km with an inclination of 88.1 degrees.
Both satellites were fully instrumented ionospheric observatories including
sweep- and fixed-frequequency ionosondes, a VLF receiver, energetic and soft
particle detectors, an ion mass spectrometer, an electrostatic analyzer, an
Langmuir probe, a beacon transmitter, a cosmic noise experiment and ISIS 2 also
carried two photometers. A tape recorder with 1-h capacity was included on both
satellites. Data were also collected during overflights of several telemetry
stations. The telemetry stations were in areas that provided primary data
coverage near the 80-deg-W meridian and in areas near Hawaii, Singapore,
Australia, the UK, Norway, India, Japan, Antarctica, New Zealand, and Central
Africa.

This ionogram was digitized from the original ISIS 2 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1995

Variable Notes

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 2 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 2 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1995

Variable Notes

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 2 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1995

Variable Notes

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 2 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1995

Variable Notes

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 2 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1995

Variable Notes

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

A 7-track ISIS 2 analog telemetry tape from Ottawa (#561) has been
digitized using the GSFC facilities of the Data Evaluation Laboratory
(DEL) within the Mission Operations and Data Systems Directorate (Code
500) at Goddard. The digitization was performed using an A/D
converter board and software device driver compatible with the OS/2
operating system used by the 486-based Programmable Telemetry
Processor (PTP) associated software has been installed on their PTP
and de-bugged so that we now have a working system for making digital
ISIS ionograms directly from the telemetry tapes. Earlier, we
successfully digitized the PCM and NASA 36 bit time-code data from
this same tape. The ionograms were digitized at the rate of 40,000
16-bit samples/sec. This sample rate is higher than the Nyquist
frequency of 30 kHz appropriate for the post-detection ISIS 2
sounder-receiver video output which extends from DC to 15 kHz (see p.
50 of the 1971 ISIS 2 report by Daniels). The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (ct/2) interval of 3.747 km. With the ISIS 2 prf of 45
sounder pulses/s, there are (1/45)/(2.5**(-5)) = 888.89 samples
between each of the approximately 1015 sounder pulses per ionogram
(including the fixed-frequency portion) or nearly 10**6 16-bit
samples/ionogram (approximately 1.8 MBytes) for just the
sounder-receiver video data. Adding header information, and the pcm
data containing data from the other instruments, yields about 2 MBytes
of data for the 22.5 s period corresponding to one ionogram. Two steps
were taken in order to reduce this large volume of nearly 2
MBytes/ionogram. First, every four 25 microsecond samples following
the sounder pulse were averaged. Second, the 16 bit samples were
reduced to 8 bit samples. The first step decreased the apparent-range
resolution to 15 km, but yielded high-quality ionograms because of the
improved S/N due to the averaging.

Modification History

created April 1995

Variable Notes

Altitude

Virtual variable.

Interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 2 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1995

Variable Notes

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 2 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1995

Variable Notes

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

This ionogram was digitized from the original ISIS 2 analog
telemetry data on 7-track tape using the facilities of the Data
Evaluation Laboratory at GSFC (Code 500). This data restoration
project is headed by Dr. R.F. Benson (GSFC, Code 692). Ionograms were
digitized at the rate of 40,000 16-bit samples/sec. This sample rate is
higher than the Nyquist frequency of 30 kHz. The sample frequency of 40
kHz provides a measurement every 25 microseconds corresponding to an
apparent range (c*t/2) interval of 3.747 km. Each ionogram consists
of a fixed-frequency and and a swept-frequency portion. The time
resolution is typically 24 seconds. More information can be found
at https://nssdc/space/isis/isis-status.html

Modification History

created April 1995

Variable Notes

interpolated fixed & sweep frequencies

This variable could be used as x-axis on amplitude spectrograms if fixed part is
subtracted.

ISIS 2 was an ionospheric observatory instrumented with a sweep- and a
fixed-frequency ionosonde, a VLF receiver, energetic and soft particle
detectors, an ion mass spectrometer, an electrostatic probe, a retarding
potential analyzer, a beacon transmitter, a cosmic noise experiment, and two
photometers. Two long crossed-dipole antennas (73 and 18.7 m) were used for the
sounding, VLF, and cosmic noise experiments.
The spacecraft was spin-stabilized to about 2 rpm after antenna deployment.
There were two basic orientation modes for the spacecraft, cartwheel and
orbit-aligned. The spacecraft operated approximately the same length of time in
each mode, remaining in one mode typically 3 to 5 months. The cartwheel mode
with the axis perpendicular to the orbit plane was made available to provide ram
and wake data for some experiments for each spin period, rather than for each
orbit period. Attitude and spin information was obtained from a three-axis
magnetometer and a sun sensor. Control of attitude and spin was possible by
means of magnetic torquing.
The experiment package also included a programmable tape recorder with a one
hour capacity. For non-recorded observations, data from satellite and
subsatellite regions were telemetered when the spacecraft was in the line of
sight of a telemetry station. Telemetry stations were located so that primary
data coverage was near the 80-deg-W meridian and near Hawaii, Singapore,
Australia, England, France, Norway, India, Japan, Antarctica, New Zealand, and
Central Africa. NASA support of the ISIS project was terminated on October 1,
1979.
A significant amount of experimental data, however, was acquired after this date
by the Canadian project team. ISIS 2 operations were terminated in Canada on
March 9, 1984. The Radio Research Laboratories (Tokyo, Japan) then requested and
received permission to reactivate ISIS 2. Regular ISIS 2 operations were started
from Kashima, Japan, in early August 1984. ISIS 2 was deactivated effective 24,
1990. A data restoration effort began in the late 1990s and successfully saved a
considerable portion of the high-resolution data before the telemetry tapes were
discarted.
The data set was generated from the averaged ionogram binary data (SPIO-00318)
recorded by the Topside Sounder. The data are obtained with the TOPIST program,
which analyzes the data, automatically scales the ionogram traces and
resonances, and inverts the traces into an electron density profile. The same
program is available for use to hand-scale the data if desired. Output data
items include spacecraft position, electron density profile, assessment of
quality, resonance and cut-off frequencies, and both the O-trace and X-trace.

This data set, provided by the Communications Research Centre (CRC) in Ottawa,
Canada, consists of electron density profiles for the ionosphere above the F2
maximum (topside ionosphere). The data were computed from the orginal ionograms
using Jackson's method (Jackson, Proceedings of the IEEE., p. 960, June 1969).
ISIS-1 was launched on 1969-01-30 into an elliptical orbit (500-3500km) with an
inclination of 88.4 degrees and ISIS-2 was launched on 1971-04-01 into an
circular orbit at 1400 km with an inclination of 88.1 degrees.
Both satellites were fully instrumented ionospheric observatories including
sweep- and fixed-frequequency ionosondes, a VLF receiver, energetic and soft
particle detectors, an ion mass spectrometer, an electrostatic analyzer, an
Langmuir probe, a beacon transmitter, a cosmic noise experiment and ISIS 2 also
carried two photometers. A tape recorder with 1-h capacity was included on both
satellites. Data were also collected during overflights of several telemetry
stations. The telemetry stations were in areas that provided primary data
coverage near the 80-deg-W meridian and in areas near Hawaii, Singapore,
Australia, the UK, Norway, India, Japan, Antarctica, New Zealand, and Central
Africa.

This 15.36s data set was created in 2008-9 at GSFC/SPDF from a newly created
320ms data set, with some gaps filled with data from the prior 15.36s data set.
Full documentation may be found at
ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/imp/imp8/mag/15s_ascii_v3/00_IMP8_1
5s_data_docum.txt. Creation of the new 320ms and 15.36s data sets was done by
N. Papitashvili and J. King, with guidance from Adam Szabo.

Modification History

Master CDF made 02/16/10 by N. E. Papitashvili, SPDF Modified to revised form
v03 on 02/16/10.

Measurements of spectra and anisotropy of electrons witin energy ranges 20-40
keV from two time-of-flight detectors EM-1-1 and EM-1-2. The field of view of
these detectors are directed oppositely and perpendicular to the satellite
rotation axis.
Data description: http://www.iki.rssi.ru/inte rball.html

The value is taken from the sensorthat can scan the angle's interval 45-180deg
or can be fixed at angles 45, 90,135, 180 deg. with respect to the sunward
directed spacecraft spin axis

Status Flag: energy and position coded, see description

Standard flags are used in the case ofdata absence. SFs are set to 11-15
and21-25 for all valid data values of each parameter. Most significant digit (1-
low or 2 - high) indicates level of the energy threshold. Higher energy
threshold will be used only in case ofdegradation of a sensor. Less significant
digit indicates sensor orientation ( 1, 2, 3, 4, 5 correspondrespectively to 45,
90, 135, 180 deg.and scan)

Status Flag: energy and positioncoded, see description

Standard flags are used in the case ofdata absence. SFs are set to 11-15
and21-25 for all valid data values ofeach parameter. Most significant digit (1-
low or 2 - high) indicates level of the energy threshold. Higher energy
threshold will be used only in case ofdegradation of a sensor. Less significant
digit indicates sensor orientation ( 1, 2, 3, 4, 5 correspondrespectively to 45,
90, 135, 180 deg.and scan)

References: 1.Troshichev O.A. et al, Planet.Space Sci., 36, 1095, 1988.
2.Vennerstrom S. et al, Report UAG-103, World Data Center A for STP, Boulder,
April 1994
PC-index is an empirical magnetic activity index based on data from single
near-pole station (Thule or Vostok for N or S hemispheres, respectively).
Its derivation procedure is optimized to achieve the best correlation of
PC-index with the solar wind electric field (SWEF) magnitude (
v*B*sin(teta/2)**2 ).
The averaged horizontal magnetic disturbance vector (quiet value subtracted) is
projected onto the optimal direction (defined empirically for each UT hour and
each season based on the best correlation with the SWEF) and, after
normalization to the equivalent value of SWEF, it gives the PC-index (expressed
in mV/m).
Although PC-index is formally expressed in mV/m, it actually represents the
measure of magnetic activity, the normalization procedure (to SWEF) helps to
reduce the seasonal/diurnal effects to facilitate the intercomparison.
The resolution of the northern cap PC-index is 5 min and of the one from
southern cap - 15 min. However, one time scale with the 5 min step is used for
both indices and each 15 min averaged value of southern index is, hence,
repeated for three times.
Full description: http://www.iki.rssi.ru/interball.html

The electron density values listed in this file are derived from the IMAGE Radio
Plasma Imager (B.W. Reinisch, PI) data using an automatic fitting program
written by Phillip Webb with manual correction.
The electron number densities were produced using an automated procedure (with
manual correction when necessary) which attempted to self-consistently fit an
enhancement in the IMAGE RPI Dynamic Spectra to either 1) the Upper Hybrid
Resonance band, 2) the Z-mode or 3) the continuum edge. The automatic algorithm
works by rules determined by comparison of the active and passive RPI data
[Benson et al., GRL, vol. 31, L20803, doi:10.1029/2004GL020847, 2004].
The manual data points are not from frequencies chosen freely by a human. Rather
the human specifies that the computer should search for a peak or continuum edge
in a certain frequency region. Thus even the manual points are determined, in
part, by the automatic algorithms. Of course that does not guarantee that the
data points are right, but it does eliminate some human bias.
For a more detailed description see .http://ulcar.uml.edu/rpi.html.

Variable Notes

Time

The time in EPOCH refers to the beginning of the spectrogram frequency sweep.

electron density

The electron number densities were derived from an automated procedure (with
manual correction when necessary) which attempted to self-consistently fit an
enhancement in the IMAGE RPI Dynamic Spectra to either 1) the Upper Hybrid
Resonance band, 2) the Z-mode or 3) the continuum edge.

model gyrofrequency

Model electron cyclotron frequency in kHz. T96 model is used for the background
magnetic field, which requires the solar wind dynamic pressure, IMF Bz, and the
DST index as input.If these parameters were not available, default values of
solar wind pressure of 2.1 nPa, IMF Bz of 0 nT, and DST of -10 nT were used

Detailed plasmagram picture has the original number of frequencies as specified
by RPI measurement parameters. Frequency axis varies from plasmagram to
plasmagram. Plasmagram *thumbnails* have a fixed frequency axis. The original
plasmagram data often requires transformation into thumbnail format by
averaging.

Actual number of ranges being measured

Number of Ranges, depending on program setting and processing.

Base Gain

TBD

BaseGain

TBD

Coupler Mode Name

values (numbers sequence only): 0= OFF (untuned), 1= ON (tuned)

Couplers

0= OFF (untuned), 1= ON (tuned)

Doppler Number to frequency translation

Translates Doppler Number to an actual Doppler Frequency. The entries are
calculated from program parameters.

DopplerTranslation

Translates Doppler Number to an actual Doppler Frequency. The entries are
calculated from program parameters.

Start MET is derived using the Nadir crossing MET and the time offset from the
first packet header. Might not be unique due to telemetry losses.

Most Probable Amplitude

Most probable amplitude

Nadir crossing MET is the reference MET that uniquely identifies all RPI measurements.

MET of the last Nadir crossing before the measurement starts.

NumDopplers

TBD

Number of Dopplers

TBD

Number of Frequencies

Detailed plasmagram picture has the original number of frequencies as specified
by RPI measurement parameters. Frequency axis varies from plasmagram to
plasmagram. Plasmagram *thumbnails* have a fixed frequency axis. The original
plasmagram data often requires transformation into thumbnail format by
averaging.

The time in EPOCH refers to the beginning of the thermal noise measurement. Use
Duration_ms to obtain stop time of the run.

Measurement duration, offset from Epoch time to the end of the measurement run.

Time in ms between start and stop of the measurement run.

Measurement start MET.

Start MET is derived using the Nadir crossing MET and the time offset from the
first packet header. Might not be unique due to telemetry losses.

Nadir crossing MET is the reference MET that uniquely identifies all RPI measurements.

MET of the last Nadir crossing before the measurement starts.

NumRepetitions

2**N, where N is RPI control parameter

Number of Frequencies

Detailed plasmagram picture has the original number of frequencies as specified
by RPI measurement parameters. Frequency axis varies from plasmagram to
plasmagram. Plasmagram *thumbnails* have a fixed frequency axis. The original
plasmagram data often requires transformation into thumbnail format by
averaging.

Number of frequencies measured

Detailed plasmagram picture has the original number of frequencies as specified
by RPI measurement parameters. Frequency axis varies from plasmagram to
plasmagram. Plasmagram *thumbnails* have a fixed frequency axis. The original
plasmagram data often requires transformation into thumbnail format by
averaging.

These files provides access to a field/plasma-merged 2-min ISEE3 data setcreated
at NSSDC as part of preparing ISEE3 data for new OMNI. Input to the data set
were 1-min MAG magnetic field data, 24-splasma data, and daily spacecraft
position data, all obtained from
theftp://spdf.gsfc.nasa.gov/pub/data/isee/isee3/ from which needed documentation
may be found. The annual files of this ASCII data set may be accessed at FTP
siteftp://spdf.gsfc.nasa.gov/pub/data/isee/isee3/2_min_merged_mag_plasma/as
well.
Time span: Mag field: 1978-09-11 - 1982-10-12 Plasma: 1978-09-11 -
1980-02-19
Note that Magntic Field is given in SE- Spacecraft-centered Solar-Ecliptic
coordinate system.

This data set contains averaged 1-minute magnetic field data converted from
simple ASCII records. It was created at NSSDC from a more complex,
multi-resolution data set (NSSDC ID = SPHE-00673; Old ID = 78-079A-02D) provided
by the Principal Investigator team and now available
fromftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/isee/isee3/magnetic_fields/1min
_ascii/
The coordinate system for the B-field components is the JPL-defined I,S
coordinate system (origin at the spacecraft): I is the unit vector in the
direction of the ISEE-3 spin axis (positive in the northward direction), and S
is the unit vector from the spacecraft to the sun. The z-axis is parallel to to
I, the y-axis to the cross-product I x S, and the x-axis to Y x Z. The I,S
coordinate system is approximately the same as the Solar Ecliptic (SE) system
since the spacecraft z-axis (the spin axis) is maintained within 0.5 degree of
perpendicular to the ecliptic plane. (SE is defined the same way as GSE, but
with the spacecraft [point of observation] substituted for Earth).
For years 1984-1990 we added spacecraft position in HGI coordinate
The HGI coordinates are Sun-centered and inertially fixed with respect to an
X-axis directed along the intersection line of theecliptic and solar equatorial
planes, and defines zero of the longitude, HGI_LONG. The solar equator plane is
inclined at 7.25degrees from the ecliptic. This direction was towards ecliptic
longitude of 74.367 deg on 1 January 1900 at 12:00 UT; because of the precession
of the Earth"s equator, this longitude increases by 1.4 deg/century. The Z-axis
is directed perpendicular to and northward of the solar equator, and the Y-axis
completes the right-handed set. The longitude, HGI_LONG increase from zero in
the X-direction towards Y-direction.The latitude HG_LAT increases to +90 deg
towards the north pole, and to -90 deg towardsm south pole.
Note that here present values averaged in 1-minute, e.g. <B>^2 may be not equal
B^2)>.

This enhanced CDF master was generated by NSSDC, with input from R. Fitzenreiter
and A. F.-Vinas, to make useable a bare-bones CDF data set provided earlier to
NSSDC. This current CDF master version, Oct. 5, 2007, is used for making a new
CDF by selecting only certain variables from those available in the original
bare-bones CDF (SPHE-00414).

Electron density at 0.5 sec resolution (60-deg sector) taken during one spin.

Electron density is obtained 6 times during a spacecraft spin period. The six
measurements are separately averaged to make the six elements of this array. We
still need to know the delta t from Epoch to the first of these 6 densities.

Data coverage includes the region from 6 earth radii out to (but excluding) the
bow shock. The reasons for selecting this area of coverage are that the solar
wind ion distributions are too cold to be adequately resolved by this
instrument, and inside the region of 6 earth radii the fast plasma data would be
contaminated by the energetic particle background.
The data are provided at a temporal resolution of approximately 60 seconds. They
represent moments of individual two-dimensional (2D) distributions obtained in
approximately 3 or approximately 6 seconds (see below). No time averaging over
longer intervals is involved; instead, the temporal resolution of the full data
set (approximately 3 / 6 / 12 s) was reduced to approximately 60 s. The UT given
indicates the start of the respective sampling interval. For a description of
the instrument see Bame et al., 1978 (IEEE Transact. Geosci. Electron. GE-16,
216) and Bame et al., 1993 (Rev. Sci. Inst., 64, 1026). Remarks about the
computation of the moments may be found in Paschmann et al., 1978 (Space Sci.
Rev. 22, 717).
The moments were computed for three 'species', but only the ion moments are
included here: lop (low-ener. ions, ~1eV/e-~130eV/e); hip (hi-ener. ions,
~130eV/e-~45keV/e); alle (electrons, ~30eV - ~45keV). The moments are computed
after the fluxes are corrected for background and s/c potential. Algorithms for
these corrections are relatively unsophisticated, so the moments are suspect
during times of high background and/or high spacecraft potential. Because the
determined spacecraft potential is not very precise, the magnitude of the
low-energy ion flow velocity is probably not accurate, but the flow direction is
well determined. Tperp and Tpara are obtained from diagonalization of the
3-dimensional temperature matrix, with the parallel direction assigned to the
eigenvalue which is most different from the other two. The corresponding
eigenvector is the symmetry axis of the distribution and should be equivalent to
the magnetic field direction. The eigenvalue ratio Tperp/Tmid, which is provided
for each species, is a measure of the symmetry of the distribution and should be
~1.0 for a good determination. Several of the parameters have a fairly high
daily dynamic range and for survey purposes are best displayed logarithmically.
These parameters are indicated by a 'SCALETYP' value of 'linear' in this file. A
quality Flag value of 1 indicates that the values are suspect because of
unreliable location info.

Modification History

This is a revised version of the data; the PI team re-processed the data and
provided this replacement version in July 1986.

Spacecraft coordinate axes normally differ by no more than a few degrees from
the respective GSE axes..The 2D bulk velocity essentially represents the
projection of the true velocity onto the symmetry plane of the analyzers, i.e.,
approximately the ecliptic plane.

Y-component of 2D bulk velocity (s/c coordinates). See VAR_NOTES.

Spacecraft coordinate axes normally differ by no more than a few degrees from
the respective GSE axes..The 2D bulk velocity essentially represents the
projection of the true velocity onto the symmetry plane of the analyzers, i.e.,
approximately the ecliptic plane.

These data are high temporal resolution solar wind ion moments derived from
measurements obtained by the Los Alamos X-Fan Solar Wind Ion Experiment (SWE) on
ISEE-1. The data cover the solar wind seasons for the spacecraft (roughly July
through December) from 1977 through 1983. The temporal resolution is 24 seconds
at high data rate and 48 seconds at low data rate. Among the parameters, the
flow azimuth is given in degrees, with 0 degrees corresponding to flow from the
sun [corrected for aberration] and positive azimuths corresponding to flow
toward dawn; flow latitude is in degrees, with positive latitudes corresponding
to flow toward the south; an alpha/proton fraction of 0.00 means no
determination was made. The data providers did not attempt to cross-calibrate
density values with those from other experiments. However, they expected that
density values will tend to be too low in later years because of detector
degradation. Cross-calibration using, for example, IMP-derived values would be a
useful exercise. Please note also that many of these measurements were obtained
within the foreshock region where the solar wind flow is affected by waves in
the foreshock.
References: Los Alamos Magnetospheric Plasma Analyzer (MPA) [Bame et al., ISEE-1
and ISEE-2 fast plasma experiment and the ISEE-1 solar wind experiment, IEEE
Trans. Geosci. Electron., GE-16, 216, 1978]; Los Alamos Magnetospheric Plasma
Analyzer (MPA) [Bame et al., Magnetospheric plasma analyzer for spacecraft with
constrained resources, Rev. Sci. Instrum., 64, 1026 (1993)].
The moments are presented in s/c coordinates: the z-axis is aligned with
the spin axis, which points radially toward the center of the Earth;
the x-axis is in the plane containing the spacecraft spin axis and the spin
axis of the Earth, with +X generally northward; and the y-axis points
generally eastward. Polar angles are measured relative to the spin axis
(+Z), and azimuthal angles are measured around the z-axis, with zero along
the +X direction. The moments are computed after the fluxes are
corrected for background and s/c potential. Algorithms for these corrections
are relatively unsophisticated, so the moments are suspect during times of
high background and/or high spacecraft potential. Because the determined
spacecraft potential is not very precise, the magnitude of the low-energy
ion flow velocity is probably not accurate, but the flow direction is well
determined.

A bitwise OR'ing of all known issue values for this record. The following issue
values are defined: (0x4: MOZER) if this flag is present then the Quasi-static
Electric Fields instrument (F. S. Mozer) is performing a bias sweep, (0x8:
HARVEY) identifies possible interference that occurs when the Plasma Density
instrument (C. C. Harvey) injects signals on either of the long electric dipole
antennas.

A bitwise OR'ing of all known issue values for this record. The following issue
values are defined: (0x1: SCAN) if this flag is present then the Medium Energy
Particles instrument's (D. J. Williams) scan platform is in operation, (0x2:
Z-MEAS) if this flag is present internally generated signals are being applied
to the search coil antennas.

Spin Axis B-Field Spectra, Bz search coil

These data are collected via the z-axis Magnetic Search Coil (Bz) which has an
upper cutoff frequency of 10 kHz. It's constructed of a 16 inch mu-metal core
and wound with 10000 turns wire. Almost 99% of all magnetic field measurements
from the PWI were collected via the Bz search coil. NOTE: When they are present
at all, the upper 6 frequency indices contain data collected above the search
coil's upper cutoff frequency. Though these data are included for completeness,
all samples above 10 kHz are *not* calibrated data and should be used with
caution. See the 'B_Quality' variable and the 'Quality_note' for issues
regarding Bz_Spectra

Spin Plane B-Field Spectra, Bu search coil

These data were collected via the U-axis Magnetic Search Coil (Bu). This coil
had the same physical properties as the Bv coil but was mounted perpendicular to
both the Bz and Bv coils. The Bu coil axis pointed along the U direction, which
is also within the spacecraft spin plane. This variable is almost always
*empty*. Less than 0.1% of magnetic spectra were collected via this search coil.
See the 'B_Quality' variable and the 'Quality_note' for issues regarding
Bu_Spectra.

Spin Plane B-Field Spectra, Bv search coil

These data were collected via the V-axis Magnetic Search Coil (Bv). This coil
had the same physical properties as the Bz coil but was mounted perpendicular to
the Bz coil. The Bv coil axis pointed along the V direction, which is within
the spacecraft spin plane. This variable is usually *empty*. Less than 2.5% of
magnetic spectra were collected via this search coil. See the 'B_Quality
variable and the 'Quality_note' for issues regarding Bu_Spectra.

Spin Plane E-Field Spectra, 215 meter long-wire antenna

These data are collected via the fine wire electric dipole antenna which had a
tip to tip length of 215 meters. The Ev antenna was used to collect over 99% of
the E-field measurements obtained by the PWI. Most of the time (98.3%) these
data were collected via the ESA (Electric Spectrum Analyzer). Though a small
fraction of the data are from the MSA (Magnetic Spectrum Analyzer). The two
analyzers have almost identical channel centers and bandwidths, except that ESA
has 6 more bands above the highest band of the MSA. When the MSA is used to
read an electric antenna, the upper 6 bands are marked with fill data. This
antenna was shared with the Heppner DC electric-field experiment. The
E_Quality' variable flags times when known spacecraft noise sources are present
in the E-field data.

Spin Plane E-Field Spectra, 73.5 meter two-sphere antenna

Less that 0.5% of electric spectra in this data set were collected via the Eu
antenna. This variable is almost always <b>empty</b>. The Eu sensor is a
two-sphere electric antenna which had a sphere-to-sphere separation of 73.5
meters. The spheres on the u-axis have a diameter of 8.0 cm and each contains a
high-impedance preamplifier which provides signals to the main electronics box
which contained the spectrum analyzers. This antenna was shared with the Mozer
quasi-static electric-field instrument. Consult the 'E_Quality' variable for
issues regarding Ev_Spectra values.

The ISEE-1 PWI ESA may be connected to one of 4 different input sources, the Eu,
Ev, and Es antennas, as well as the Bz search coil. Only electric spectra are
provided in this file series. Since the Es antenna was used to provide less than
0.01% of the electric wave measurements and since Es data exhibit a very low
sensitivity range, these have been dropped from the CDF archive. This leaves
only Eu, or Ev data in the E_spectra variable. The Ev antenna was connected to
the ESA 98.3% of the time, while the Eu antenna was utilized less than 0.5% of
the time. If the Eu antenna contributed any of the measurements for a sweep
then the 'Eu_Sensor' flag is set to 1. If not this flag reads 0.

A bitwise OR'ing of all known issue values for this record. The following issue
values are defined: (0x4: MOZER) if this flag is present then the Quasi-static
Electric Fields instrument (F. S. Mozer) is performing a bias sweep, (0x8:
HARVEY) identifies possible interference that occurs when the Plasma Density
instrument (C. C. Harvey) injects signals on either of the long electric dipole
antennas.

SA Channel Center Frequency

These are the frequency channels for the 16 upper Electric Spectrum Analyzer
(ESA) bands. Rapid sample data were not collected using the first 4 bands of
the ESA.

Spin Plane E-Field Spectral Density, 56.2 Hz to 311 kHz

These data are collected primarily via the fine wire electric dipole antenna
which had a tip to tip length of 215 meters. A small fraction of the data in
this variable were collected via the Eu antenna. See the 'Eu_Sensor' variable
to distinguish the input sources if needed. The Eu and Ev antennas were shared
with the Heppner DC electric-field experiment. Consult the 'Quality_Flag
variable for issues regarding E_Series values.

These are the frequency channels for all 4 of the SFR bands. The SFR outputs 4
simultaneous measurements, one for each band. In this file those measurements
have been reordered by increasing frequency. If needed, the the sub-sweep time
of each point may be determined using the SubSweepTime variable.

Eu_Sensor

The ISEE-1 PWI SFR may be connected to one of 4 different input sources, the Eu,
Ev, and Es antennas, as well as the Bz search coil. Data collected via the Bz
antenna are provided in a separate file. Since the Es antenna was used to
provide less that 0.01% of the electric wave measurements and since Es data
exhibit a very low sensitivity range, these have been dropped from the CDF
archive. This leaves only Eu, or Ev data in the E_spectra variable. The Ev
antenna was connected to the SFR 98.3% of the time, while the Eu antenna was
utilized less than 0.5% of the time. If the Eu antenna contributed any of the
measurements for a sweep then the 'Eu_Sensor' flag is set to 1. If not this
flag reads 0.

Event time for the start of the sweep

Spacecraft Event Time in UTC for the start of an SFR sweep. To get time offsets
within a sweep add the corresponding values in the SubSweepTime array.

A bitwise OR'ing of all known issue values for this record. The following issue
values are defined: (0x4: MOZER) if this flag is present then the Quasi-static
Electric Fields instrument (F. S. Mozer) is performing a bias sweep, (0x8:
HARVEY) identifies possible interference that occurs when the Plasma Density
instrument (C. C. Harvey) injects signals on either of the long electric dipole
antennas.

Spin Plane E-Field Spectra, 104 Hz to 347 kHz

These data are collected primarily via the fine wire electric dipole antenna
which had a tip to tip length of 215 meters. A small fraction of the data, less
that 0.5%, in this variable were collected via the Eu and Es antennas. See the
Eu_Sensor' variable to distinguish the input sources if needed. The Eu and Ev
antennas ware shared with the Heppner DC electric-field experiment. Consult the
Quality_Flag' variable for issues regarding E_Spectra values.

Time offsets from the Epoch time for each spectral measurement in a sweep

If sub-sweep timing is not important to your application, this value can be
ignored. Otherwise for each measurement add this time to the Epoch value for the
record. There is one offset in this array for each measurement in the SFR sweep

When set to 1 PWI is in 4x sample rate mode

ISEE-1 Could operate in two telemetry modes, called 'low bit rate' and 'high bit
rate'. Low bit rate was more common. During low-bit rate the SFR outputs were
sampled once per second. In high bit rate mode sampling was preformed 4 times
per second. In either case the SFR center frequencies were only changed
1/second. This means that an entire sweep always requires 32 seconds to
preform. To keep records consistent across both telemetry modes, in this data
set 4 samples taken at a single frequency over the same second are averaged
together during high rate telemetry operations. When this flag = 1 each data
point is a 4-sample average, when set to0 each data point represents a single
A/D conversion on-board ISEE-1

Data coverage includes the region from 6 earth radii out to (but excluding) the
bow shock. The reasons for selecting this area of coverage are that the solar
wind ion distributions are too cold to be adequately resolved by this
instrument, and inside the region of 6 earth radii the fast plasma data would be
contaminated by the energetic particle background.
The data are provided at a temporal resolution of approximately 60 seconds. They
represent moments of individual two-dimensional (2D) distributions obtained in
approximately 3 or approximately 6 seconds (see below). No time averaging over
longer intervals is involved; instead, the temporal resolution of the full data
set (approximately 3 / 6 / 12 s) was reduced to approximately 60 s. The UT given
indicates the start of the respective sampling interval. For a description of
the instrument see Bame et al., 1978 (IEEE Transact. Geosci. Electron. GE-16,
216) and Bame et al., 1993 (Rev. Sci. Inst., 64, 1026). Remarks about the
computation of the moments may be found in Paschmann et al., 1978 (Space Sci.
Rev. 22, 717).
The moments were computed for three 'species', but only the ion moments are
included here: lop (low-ener. ions, ~1eV/e-~130eV/e); hip (hi-ener. ions,
~130eV/e-~45keV/e); alle (electrons, ~30eV - ~45keV). The moments are computed
after the fluxes are corrected for background and s/c potential. Algorithms for
these corrections are relatively unsophisticated, so the moments are suspect
during times of high background and/or high spacecraft potential. Because the
determined spacecraft potential is not very precise, the magnitude of the
low-energy ion flow velocity is probably not accurate, but the flow direction is
well determined. Tperp and Tpara are obtained from diagonalization of the
3-dimensional temperature matrix, with the parallel direction assigned to the
eigenvalue which is most different from the other two. The corresponding
eigenvector is the symmetry axis of the distribution and should be equivalent to
the magnetic field direction. The eigenvalue ratio Tperp/Tmid, which is provided
for each species, is a measure of the symmetry of the distribution and should be
~1.0 for a good determination. Several of the parameters have a fairly high
daily dynamic range and for survey purposes are best displayed logarithmically.
These parameters are indicated by a 'SCALETYP' value of 'log' in this file. A
quality Flag value of 1 indicates that the values are suspect because of
unreliable location info.

Modification History

This is a revised version of the data; the PI team re-processed the data and
provided this replacement version in July 1986.

Spacecraft coordinate axes normally differ by no more than a few degrees from
the respective GSE axes..The 2D bulk velocity essentially represents the
projection of the true velocity onto the symmetry plane of the analyzers, i.e.,
approximately the ecliptic plane.

Y-component of 2D bulk velocity (s/c coordinates). See VAR_NOTES.

Spacecraft coordinate axes normally differ by no more than a few degrees from
the respective GSE axes..The 2D bulk velocity essentially represents the
projection of the true velocity onto the symmetry plane of the analyzers, i.e.,
approximately the ecliptic plane.

Magnetic field measurements on the Interball- Tail satellites
are carried out by IZMIRAN and Space Research Institute RAS (SRI)
since 1995. Satellite has the orbits with apogee 200000 (30 Re) and
perigee 500 km. and provides measurements in the solar wind and in the different
regions of the magnetosphere at the same time with Geotail, Polar and
Interbal-A working in the magnetosphere and Wind, ACE in the solar wind.
Magnetic field measurements on-board the Interball Tail Probe are
carried out by the FM-3I and MFI instruments. FM-3I consists of two flux-gate
magnetometers M1 and M2 covering two different ranges: 200 nT and
1000 nT. The M2 instrument is mostly used to perform the attitude
control of the INTERBALL TAIL spacecraft. M1 magnetometer data are
transmitted to the scientific SSNI telemetry system at rates 0.125-16
vectors/s
depending on the instrument operating mode. The magnetic field data from
the M2 magnetometer are transmitted at the rate 1 vectors per 6 sec. to the
BNS attitude control system. MFI magnetometer has the next parameters:
measured range 0.3-37.5 nT, frequency range 0-2 Hz, sampling rate from 1/4
to 8 measurements per second. FM-3 M2 magnetometer failed in February
1996, FM-3 M1 and MFI are working until now.
Data presented here are the combination of the data of all
magnetometers. First of all FM-3 M1 data are used, if they are absent, used
MFI data
and if data of both magnetometer are absent, FM-3 M2 data presented. In
case of FM-3 M1 and MFI, data are averaged for 6 seconds intervals.

Standard flags are used in case of data absence. For the valid data SF is in the
range 10-38. Most significant digit (1-3) shows energy range used. Least
significant digit shows number of the plate, data from which are used.

Electron and proton sensors of EV-3 subsystem are offset at an angle 135 deg
with respect to the sunward directed spacecraft spin axis

Electron Flux, 21-26 keV (DOK-2 first electron sensor, fixed)

sensor offset at an angle 180 deg with respect to the sunward directed
spacecraft spin axis

Electron Flux, 76-95 keV (DOK-2 first electron sensor, fixed)

sensor offset at an angle 180 deg with respect to the sunward directed
spacecraft spin axis

Proton Flux, 1-3 MeV (SKA-2 proton sensor)

Electron and proton sensors of EV-3 subsystem are offset at an angle 135 deg
with respect to the sunward directed spacecraft spin axis

Proton Flux, 21-27 keV (DOK-2 second proton sensor, scan)

The value is taken from the sensor that can scan the angle's interval 45-180 deg
or can be fixed at angles 45, 90, 135, 180 deg. with respect to the sunward
directed spacecraft spin axis

Proton Flux, 22-28 keV (DOK-2 first proton sensor, fixed)

sensor offset at an angle 180 deg with respect to the sunward directed
spacecraft spin axis

Status Flag: energy and position coded, see description

Standard flags are used in the case of data absence. SFs are set to 11-15 and
21-25 for all valid data values of each parameter. Most significant digit (1 -
low or 2 - high) indicates level of the energy threshold. Higher energy
threshold will be used only in case of degradation of a sensor. Less significant
digit indicates sensor orientation ( 1, 2, 3, 4, 5 correspond respectively to
45, 90, 135, 180 deg. and scan)

Status Flag: standard values, see description

Standard flags are used in the case of data absence. SFs are set to 11-15 and
21-25 for all valid data values of each parameter. Most significant digit (1 -
low or 2 - high) indicates level of the energy threshold. Higher energy
threshold will be used only in case of degradation of a sensor. Less significant
digit indicates sensor orientation ( 1, 2, 3, 4, 5 correspond respectively to
45, 90, 135, 180 deg. and scan)